FieldDxMalignant catarrhClinical signs, differential diagnosis, treatment and prevention in cattle, buffalo and pigs.
Overview
A fatal lymphoproliferative disease of cattle and other susceptible ungulates, transmitted from an inapparently-infected carrier species. Ruminant gammaherpesviruses of the Macavirus genus -- chiefly ovine herpesvirus 2 (from sheep) and alcelaphine herpesvirus 1 (from wildebeest); carriers show no disease, but transmit it to susceptible species such as cattle.
Clinical signs
- Highly fatal systemic disease with mortality rates in clinically affected animals approaching 95%.
- Head-and-Eye Form (Cattle): Sudden onset of extreme dejection, anorexia, agalactia, and persistent high fever (41° to 41.5°C 106°–107°F).
- Severe conjunctivitis and progressive bilateral corneal edema (corneoscleral opacity starting at the limbus and moving centrally).
- Profuse, thick, mucopurulent nasal discharge, severe dyspnea with stertor, increased salivation with ropes of saliva hanging from the mouth, and severe diffuse intensely hyperemic, erosive, and necrotizing stomatitis…
- Lymphadenopathy (enlargement of all superficial lymph nodes), hematuria, skin lesions (necrotic scabs on perineum, udder, inner thighs, axillae; moist eczema
- Pigs: Nonspecific signs including depression, anorexia, high fever, recumbency, abnormal respiration, and scant hard mucus-covered feces.
- Neurologic signs develop: ataxia, tremors, convulsions, dog-sitting posture, forelimb paralysis, and aggressive behavior.
- Corneal edema with severe uveitis, bilateral corneal opacity, excessive lacrimation, and eyelid thickening cause blindness.
Predisposing factors
- Exposure or close contact with reservoir carrier species: blue wildebeest (Connochaetes taurinus) for blue wildebeest-associated MCF (AlHV-1), or sheep, particularly weaned lambs/adolescent sheep…
- Peak incidence occurs in late winter, spring, and summer.
- Copper deficiency or bracken fern exposure may act as environmental stressors that predispose cattle to the disease.
- In pigs, keeping pigs together with sheep (e.g., in traveling circuses or mixed housing) is a major risk factor.
Look-alikes to rule out
Treatment
- No treatment has been found to provide any consistent benefit; the prognosis is grave.
- Supportive care and stress reduction of subclinical or mildly affected animals are indicated.
- In pigs, antibiotics may temporarily reduce the severity of secondary bacterial infection.
Prevention
1. Avoid any contact between susceptible species (cattle, bison, deer, pigs) and reservoir carrier hosts (sheep, goats, wildebeest). 2. For highly susceptible species like bison, separation distances of greater than 1 km from lamb feedlots may be necessary to prevent airborne transmission. 3.
Source
A Textbook of the Diseases of Cattle, Horses, Sheep, Pigs and Goat by ELSEVIER (Pages 2076–2080); The Merck Veterinary Manual 11th Edition (Pages 905–909); A Textbook of the Diseases of Cattle, Horses, Sheep, Pigs and Goat by ELSEVIER (Pages 996, index 2302); Preventive Veterinary Medicine by ICAR (Pages 316-317).
MSD Veterinary Manual — Malignant Catarrhal Fever in Animals (accessed 2026-08-11)
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